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Regenerative Drives - Effect of Power Factor

Former Community Member
Former Community Member

I am working on a small 16kW hydro system which is experiencing about 15% loss in the Regenerative VSD. To maximise efficiency the turbine operates at variable speed. The VSD controls a synchronous generator and supplies the grid.

The VSD is a Siemens G120. The datasheet states that the efficiency should be around 96%, whilst also stating that the Power Factor is 0.9. I am looking to replace this drive for an ABB ACS 880-11 which has similar efficiency but a unity power factor.

Firstly can I trust these datasheets since, I assume, they relate to the VSD delivering electrical energy to a motor rather receiving it from a generator? Is there an efficiency penalty for regenerative generation?

Secondly, with all else being equal, will the drive with a unity power factor equate to more electrical energy on the meter than the drive with a 0.9 power factor? 

Thanks

 

 

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  • 0

    That last part about no heat is key - ‘follow the smoke’  - If there isn't any it probably is being more efficient than you think - 2kW is a fan heater or a kettle full - hard to miss in a closed box ?

     Depending on the VSD design, the internal switching waveforms are far from sinusoidal, and it may be that by the time things are measured on the outside, some assumptions about current and voltage waveforms being in step and pure sines is confusing the calculation. Not all meters, even ‘proper’ export electricity meters read the VA of non-sine waveforms very well, and a 10% error is quite credible. (some  light reading on how your leccy bill can be cocked up by electronic loads)

    ABB and Siemens both have capable technical help, it may be sensible to get their opinions for this rather unusual case  before embarking on what may be a bit of a wild goose chase.

    Mike

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  • 0

    That last part about no heat is key - ‘follow the smoke’  - If there isn't any it probably is being more efficient than you think - 2kW is a fan heater or a kettle full - hard to miss in a closed box ?

     Depending on the VSD design, the internal switching waveforms are far from sinusoidal, and it may be that by the time things are measured on the outside, some assumptions about current and voltage waveforms being in step and pure sines is confusing the calculation. Not all meters, even ‘proper’ export electricity meters read the VA of non-sine waveforms very well, and a 10% error is quite credible. (some  light reading on how your leccy bill can be cocked up by electronic loads)

    ABB and Siemens both have capable technical help, it may be sensible to get their opinions for this rather unusual case  before embarking on what may be a bit of a wild goose chase.

    Mike

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